Hereditary nasal parakeratosis (HNPK) is a genodermatosis of Labrador Retrievers with a monogenic autosomal recessive inheritance (Pagé et al. 2003, Peters et al. 2003). HNPK-affected dogs develop crusts and fissuring of the nasal planum at a young age but are otherwise healthy. Histopathological changes consist of parakeratotic hyperkeratosis and an accumulation of proteinacious fluid (“serum lakes”) within the stratum corneum and the superficial stratum spinosum. HNPK currently cannot be cured, but the symptoms can be alleviated with symptomatic therapy.
Due to monogenic autosomal recessive inheritance, a method to determine the genotype of a dog is of high importance. Heterozygous dogs are not affected and can phenotypically not be distinguished from homozygous free dogs. However, heterozygous dogs carry the mutant allele (“carriers”) and may transmit this disease to their offspring.
At the moment breeders can identify carrier dogs only based on phenotype information collected from earlier generations and to eliminate the identified carriers from breeding programs, thereby reducing the frequency of genetic disease in a breed. Thus, there is a long felt need in the breeding of Labrador Retrievers for a genetic test that permits the identification of also healthy carriers of HNPK. Therefore, a genetic test method that can discriminate the three genotypes “free” (=homozygous wildtype), “carrier” (=heterozygous”), and “affected” (=homozygous mutant) is highly valuable for dog breeding as well as for veterinary medicine to confirm the diagnosis of suspicious cases.